Rechargeable lithium batteries are attractive energy storage devices for portable electric and electronic devices and electric and hybrid-electric vehicles because of their high specific energy compared to other electrochemical energy storage devices. A typical lithium cell contains a negative electrode, a positive electrode, and a separator located between the negative and positive electrodes. Both electrodes contain active materials that react with lithium reversibly. In some cases, the negative electrode may include lithium metal, which can be electrochemically dissolved and deposited reversibly. The separator contains an electrolyte with a lithium cation, and serves as a physical barrier between the electrodes such that none of the electrodes are electrically connected within the cell.
Typically, during charging, there is generation of electrons at the positive electrode and consumption of an equal amount of electrons at the negative electrode. During discharging, opposite reactions occur.
Over the life of an electrochemical cell, the charge capacity can be lost due to side reactions and/or active material loss. For example, undesirable side reactions occur during repeated charge/discharge cycles of the battery. These undesirable side reactions result in the reduction of the capacity of the battery to provide and store power. This also results in changes in the relationship between the “open circuit potential” (OCP) and charge capacity of the cell.